Single complex electrogram display having a sensing threshold for an implantable medical device

ABSTRACT

The present invention discloses a graphical display method and apparatus relating to an electrogram signal received from at least one lead used in conjunction with an implantable medical device. The present invention provides a time-expanded waveform of a portion of a signal relating to a single heartbeat. Sensitivity threshold information is also graphically displayed on the waveform. The programmer assembly of the present invention comprises an analyzer for locating and marking desired characteristics of the electrogram signal with a plurality of markers to produce a marked electrogram signal. A processor receives the electrogram signal from the analyzer and recognizes the marked desired characteristics of the electrogram signal. The processor also receives sensitivity threshold information from a particular lead. A display, controlled by the processor, graphically displays information representing a portion of the electrogram signal immediately adjacent to a single marker and graphically displays a sensitivity threshold superimposed onto the portion of the electrogram signal.

This application is a division of application Ser. No. 09/316,750, filedMay 21, 1999, now U.S. Pat. No. 6,266,555. This application claims thebenefit of U.S. provisional application Ser. No. 60/084,580, filed May7, 1998.

FIELD OF THE INVENTION

The present invention relates generally to a programmer used inconjunction with an implantable medical device. More specifically, thepresent invention relates to an improved graphical display of selectedinformation in conjunction with an implantable medical device.

BACKGROUND OF THE INVENTION

Implantable medical device systems known in the art comprise severalcomponents, including an implantable medical device, such as apacemaker, pacing and/or sensing leads (leads), and a programmer. Theleads connect the implantable medical device to the heart of a patient.The programmer provides multiple functions, including (a) assessing leadperformance during a pacemaker or defibrillator implantation, (b)programming the implantable medical device, and (c) receiving feedbackinformation from the implantable medical device for use by a clinicianor physician (operator). By measuring the electrical performance of alead, the programmer aids the operator in selecting an electricallyappropriate site for the placement of the lead(s).

In conjunction with programming the implantable medical device system,it is critical for an operator to determine whether the leads areproperly positioned within a passageway of a heart, such as an atrium orventricle of the patient.

A disadvantage of prior art programmers involves the techniques used todisplay information to the operator during an implant procedure. Mostprior art systems graphically display several, continuous-timewaveforms, which are constantly scrolling across the screen at a rapidrate. The remaining information is presented to the operator in the formof numerical data. In order to determine if a specific lead is properlypositioned within a passageway of the heart, the operator must reviewnot only the graphical display of the continuous-time cardiac waveformscrolling across the display, but also review a variety of numericaldata. The operator must then have the ability and understanding toprocess the various data shown both graphically and numerically in orderto determine if the lead is positioned to ensure proper operation of alater attached implantable medical device.

U.S. Pat. No. 5,713,937 to Nappholz et al. discloses a pacemakerprogrammer menu with selectable real or simulated implant data graphics.This reference discloses a graphical display of two separatecharacteristics of an implantable medical device system, such as aheartbeat of a patient and a ventricular pacing rate as applied to amedical implant.

Other disclosures relating to the same general issues are listed belowin Table 1.

TABLE 1 Prior Art Patents U.S. Pat. No. Title 5,833,623 System AndMethod For Facilitating Rapid Retrieval And Evaluation Of DiagnosticData Stored By An Implantable Medical Device 5,782,890 Method For HeartTransplant Monitoring And Analog Telemetry Calibration 5,724,985 UserInterface For An Implantable Medical Device Using An IntegratedDigitizer Display Screen 5,716,384 Method And System For Organizing,Viewing And Manipulating Information In Implantable Device Programmer5,402,794 Method And Apparatus For Heart Transplant Monitoring AndAnalog Telemetry Calibration 5,374,282 Automatic Sensitivity Adjust ForCardiac Pacemakers 5,345,362 Portable Computer Apparatus WithArticulating Display Panel 4,809,697 Interactive Programming AndDiagnostic System For Use With Implantable Pacemaker 4,374,382 MarkerChannel Telemetry System For A Medical Device Des. Portable ComputerWith An Articulating Display Panel   358,583

The prior art in general, as well as the Nappholz et al. reference inparticular, have certain disadvantages. For example, the display unitsof the prior art patents display a continuous-time cardiac waveform.This waveform is continuously scrolling across the display. Once thecontinuous-time waveform reaches the end of the display, the waveformdisappears and a new continuous-time waveform is generated in real timeand scrolls across the screen. Thus, it is virtually impossible for anoperator to determine the configuration of the waveform signal, or todetermine the amplitude of the signal. Additionally, the operator mustevaluate various numerical data in conjunction with the graphicaldisplay to determine if a specific lead is properly positioned.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art byproviding a method of and apparatus for graphically displaying a visualassessment necessary to determine proper positioning of pacing and/orsensing leads of an implantable medical device system.

The present invention has certain objects. That is, the presentinvention provides solutions to certain problems existing in the priorart such as: (a) an inability to provide a graphical display of a singlecardiac waveform representing a specific portion of the continuous-timewaveform corresponding to a single heartbeat, centered on the display;(b) an inability to update the single cardiac waveform based upon acomparison of the heart rate of the patient to specific predeterminedrates; (c) an inability to provide a graphical display of the magnitudeof the single cardiac waveform; (d) an inability to provide thegraphical display of a chosen sensitivity threshold in conjunction witha single cardiac waveform; (e) an inability to provide a graphicaldisplay of changes in the sensitivity threshold in conjunction with asingle cardiac waveform; (f) an inability to hold the single cardiacwaveform, centered on the display; and (g) an inability to print thesingle cardiac waveform.

The system and method of the present invention provides certainadvantages, including: (a) the ability to provide a graphical display ofa single cardiac waveform representing a specific portion of thecontinuous-time waveform corresponding to a single heartbeat centered onthe display; (b) the ability to update the cardiac waveform based upon acomparison of the heart rate to specific predetermined rates; (c) theability to provide a graphical display of the magnitude of the singlecardiac waveform; (d) the ability to provide a graphical display of achosen sensitivity threshold in conjunction with a single cardiacwaveform; (e) the ability to provide a graphical display of changes inthe sensitivity threshold in conjunction with a single cardiac waveform;(h) the ability to hold the single cardiac waveform centered on thedisplay; and (i) the ability to print the single cardiac waveform.

The system and method of the present invention has certain features,including a graphical display of a single cardiac waveform representinga specific portion of the continuous-time waveform corresponding to asingle heartbeat at a time during a pacemaker implant. In addition, thepresent invention permits selection of the heart passageway from whichto view the waveform. Another feature of the present invention is agraphical display of the voltage magnitude of the single cardiacwaveform, as well as an expanded version of the single cardiac waveformused to determine the proper position of a lead. Another feature of thepresent invention is the ability to utilize the heart rate of thepatient such that the single cardiac waveform is continuously updated ina manner in which an operator can view the waveform to determine properlocation of a pacing or sensing lead. Another feature of the presentinvention is a graphical representation of a chosen sensing thresholdsuperimposed onto a single cardiac waveform to assist in positioning ofa pacing or sensing lead. Another feature of the present invention isthe ability to graphically display an updated and modified sensingthreshold. Another feature of the present invention is the ability tofreeze the single cardiac waveform and superimposed sensing thresholdand print a single cardiac waveform and superimposed sensing thresholdfor further analysis.

Other objects, advantages, and features of the invention will becomeapparent by referring to the appended drawings, detailed description,and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic view of one embodiment of animplantable medical device.

FIG. 2 is a simplified illustration of an implantable medical devicewith leads positioned within passageways of a heart.

FIG. 3 is a block diagram illustrating the constituent components of animplantable medical device.

FIG. 4 is a simplified schematic view of an implantable medical devicewith leads positioned within passageways of a heart.

FIG. 5 is a partial block diagram illustrating one embodiment of animplantable medical device used in conjunction with the presentinvention.

FIG. 6 is a perspective view of a programmer unit used in conjunctionwith an implantable medical device.

FIG. 7 is a block diagram encompassing the present invention.

FIG. 8 is a pictorial representation of a typical display screen duringan implant procedure showing a plurality of continuous-time waveforms.

FIG. 9 is a second pictorial representation of a typical display screenduring an implant procedure showing a waveform area and waveform controlarea.

FIG. 10 is a pictorial representation of a display screen during animplant procedure showing a single complex cardiac waveform.

FIG. 11 is a second pictorial representation of a display screen duringan implant procedure showing a single complex cardiac waveform.

FIG. 12 is a third pictorial representation of a display screen duringan implant procedure showing a single complex cardiac waveform.

FIG. 13 is a flow chart disclosing the steps of the sensitivitythreshold feature of the present invention.

DETAILED DESCRIPTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings which form a part hereof,and in which is shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural or logical changes may bemade without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

FIG. 1 is a simplified schematic view of one embodiment of implantablemedical device (“IMD”) 10 of the present invention. IMD 10 shown in FIG.1 is a pacemaker comprising at least one of pacing and sensing leads 16and 18 attached to connector module 12 of hermetically sealed enclosure14 and implanted near human or mammalian heart 8. Pacing and sensingleads 16 and 18 sense electrical signals attendant to the depolarizationand repolarization of the heart 8, and further provide pacing pulses forcausing depolarization of cardiac tissue in the vicinity of the distalends thereof. Leads 16 and 18 may have unipolar or bipolar electrodesdisposed thereon, as is well known in the art. Examples of IMD 10include implantable cardiac pacemakers disclosed in U.S. Pat. No.5,158,078 to Bennett et al., U.S. Pat. No. 5,312,453 to Shelton et al.,or U.S. Pat. No. 5,144,949 to Olson, all hereby incorporated byreference herein, each in its respective entirety.

FIG. 2 shows connector module 12 and hermetically sealed enclosure 14 ofIMD 10 located in and near human or mammalian heart 8. Atrial andventricular pacing leads 16 and 18 extend from connector module 12 tothe right atrium and ventricle, respectively, of heart 8. Atrialelectrodes 20 and 21 disposed at the distal end of atrial pacing lead 16are located in the right atrium. Ventricular electrodes 28 and 29disposed at the distal end of ventricular pacing lead 18 are located inthe right ventricle.

FIG. 3 shows a block diagram illustrating the constituent components ofIMD 10 in accordance with one embodiment of the present invention, whereIMD 10 is a pacemaker having a microprocessor-based architecture. IMD 10is shown as including activity sensor or accelerometer 11, which ispreferably a piezoceramic accelerometer bonded to a hybrid circuitlocated inside enclosure 14 (shown in FIGS. 1 and 2). Activity sensor 11typically (although not necessarily) provides a sensor output thatvaries as a function of a measured parameter relating to a patient'smetabolic requirements. For the sake of convenience, IMD 10 in FIG. 3 isshown with lead 18 only connected thereto. However, it is understoodthat similar circuitry and connections not explicitly shown in FIG. 3apply to lead 16 (shown in FIGS. 1 and 2).

IMD 10 in FIG. 3 is most preferably programmable by means of an externalprogramming unit (shown in FIG. 6). One such programmer is thecommercially available Medtronic Model 9790 programmer, which ismicroprocessor-based and provides a series of encoded signals to IMD 10,typically through a programming head which transmits or telemetersradio-frequency (RF) encoded signals to IMD 10. Such a telemetry systemis described in U.S. Pat. No. 5,312,453 to Wyborny et al., herebyincorporated by reference herein in its entirety. The programmingmethodology disclosed in Wyborny et al.'s '453 patent is identifiedherein for illustrative purposes only. Any of a number of suitableprogramming and telemetry methodologies known in the art may be employedso long as the desired information is transmitted to and from thepacemaker.

As shown in FIG. 3, lead 18 is coupled to node 50 in IMD 10 throughinput capacitor 52. Activity sensor or accelerometer 11 is mostpreferably attached to a hybrid circuit located inside hermeticallysealed enclosure 14 of IMD 10. The output signal provided by activitysensor 11 is coupled to input/output circuit 54. Input/output circuit 54contains analog circuits for interfacing with heart 8, activity sensor11, antenna 56 and circuits for the application of stimulating pulses toheart 8. The rate of heart 8 is controlled by software-implementedalgorithms stored within microcomputer circuit 58.

Microcomputer circuit 58 preferably comprises on-board circuit 60 andoff-board circuit 62. Circuit 58 may correspond to a microcomputercircuit disclosed in U.S. Pat. No. 5,312,453 to Shelton et al., herebyincorporated by reference herein in its entirety. On-board circuit 60preferably includes microprocessor 64, system clock circuit 66 andon-board RAM 68 and ROM 70. Off-board circuit 62 preferably comprises aRAM/ROM unit. On-board circuit 60 and off-board circuit 62 are eachcoupled by data communication bus 72 to digital controller/timer circuit74. Microcomputer circuit 58 may comprise a custom integrated circuitdevice augmented by standard RAM/ROM components.

Electrical components shown in FIG. 3 are powered by an appropriateimplantable battery power source 76 in accordance with common practicein the art. For the sake of clarity, the coupling of battery power tothe various components of IMD 10 is not shown in the Figures.

Antenna 56 is connected to input/output circuit 54 to permituplink/downlink telemetry through RF transmitter and receiver telemetryunit 78. By way of example, telemetry unit 78 may correspond to thatdisclosed in U.S. Pat. No. 4,566,063 issued to Thompson et al., herebyincorporated by reference herein in its entirety, or to that disclosedin the above-referenced '453 patent to Wyborny et al. It is generallypreferred that the particular programming and telemetry scheme selectedpermit the entry and storage of cardiac rate-response parameters. Thespecific embodiments of antenna 56, input/output circuit 54 andtelemetry unit 78 presented herein are shown for illustrative purposesonly, and are not intended to limit the scope of the present invention.

Continuing to refer to FIG. 3, V_(REF) and Bias circuit 82 mostpreferably generates stable voltage reference and bias currents foranalog circuits included in input/output circuit 54. Analog-to-digitalconverter (ADC) and multiplexer unit 84 digitizes analog signals andvoltages to provide “real-time” telemetry intracardiac signals andbattery end-of-life (EOL) replacement functions. Operating commands forcontrolling the timing of IMD 10 are coupled from microprocessor 64 viadata bus 72 to digital controller/timer circuit 74, where digital timersand counters establish the overall escape interval of the IMD 10 as wellas various refractory, blanking and other timing windows for controllingthe operation of peripheral components disposed within input/outputcircuit 54.

Digital controller/timer circuit 74 is preferably coupled to sensingcircuitry, including sense amplifier 88, peak sense and thresholdmeasurement unit 90 and comparator/threshold detector 92. Circuit 74 isfurther preferably coupled to electrogram (EGM) amplifier 94 forreceiving amplified and processed signals sensed by lead 18. Senseamplifier 88 amplifies sensed electrical cardiac signals and provides anamplified signal to peak sense and threshold measurement circuitry 90,which in turn provides an indication of peak sensed voltages andmeasured sense amplifier threshold voltages on multiple conductor signalpath 67 to digital controller/timer circuit 74. An amplified senseamplifier signal is also provided to comparator/threshold detector 92.By way of example, sense amplifier 88 may correspond to that disclosedin U.S. Pat. No. 4,379,459 to Stein, hereby incorporated by referenceherein in its entirety.

The electrogram signal provided by EGM amplifier 94 is employed when IMD10 is being interrogated by an external programmer to transmit arepresentation of a cardiac analog electrogram. See, for example, U.S.Pat. No. 4,556,063 to Thompson et al., hereby incorporated by referenceherein in its entirety. Output pulse generator 96 provides amplifiedpacing stimuli to patient's heart 8 through coupling capacitor 98 inresponse to a pacing trigger signal provided by digital controller/timercircuit 74 each time either (a) the escape interval times out, (b) anexternally transmitted pacing command is received, or (c) in response toother stored commands as is well known in the pacing art. By way ofexample, output amplifier 96 may correspond generally to an outputamplifier disclosed in U.S. Pat. No. 4,476,868 to Thompson, herebyincorporated by reference herein in its entirety.

The specific embodiments of sense amplifier 88, output pulse generator96 and EGM amplifier 94 identified herein are presented for illustrativepurposes only, and are not intended to be limiting in respect of thescope of the present invention. The specific embodiments of suchcircuits may not be critical to practicing some embodiments of thepresent invention so long as they provide means for generating astimulating pulse and are capable of providing signals indicative ofnatural or stimulated contractions of heart 8.

In some preferred embodiments of the present invention, IMD 10 mayoperate in various non-rate-responsive modes, including, but not limitedto, DDD, DDI, VVI, VOO and VVT modes. In other preferred embodiments ofthe present invention, IMD 10 may operate in various rate-responsivemodes, including, but not limited to, DDDR, DDIR, VVIR, VOOR and VVTRmodes. Some embodiments of the present invention are capable ofoperating in both non-rate-responsive and rate responsive modes.Moreover, in various embodiments of the present invention IMD 10 may beprogrammably configured to operate so that it varies the rate at whichit delivers stimulating pulses to heart 8 in response to one or moreselected sensor outputs being generated. Numerous pacemaker features andfunctions not explicitly mentioned herein may be incorporated into IMD10 while remaining within the scope of the present invention.

The present invention is not limited in scope to single-sensor ordual-sensor pacemakers, and is not limited to IMD's comprising activityor pressure sensors only. Nor is the present invention limited in scopeto single-chamber pacemakers, single-chamber leads for pacemakers orsingle-sensor or dual-sensor leads for pacemakers. Thus, variousembodiments of the present invention may be practiced in conjunctionwith one or more leads or with multiple-chamber pacemakers, for example.At least some embodiments of the present invention may be appliedequally well in the contexts of single-, dual-, triple- orquadruple-chamber pacemakers or other types of IMD's. See, for example,U.S. Pat. No. 5,800,465 to Thompson et al., hereby incorporated byreference herein in its entirety, as are all U.S. patents referencedtherein.

IMD 10 may also be a pacemaker-cardioverter-defibrillator (“PCD”)corresponding to any of numerous commercially available implantablePCD's. Various embodiments of the present invention may be practiced inconjunction with PCD's such as those disclosed in U.S. Pat. No.5,545,186 to Olson et al., U.S. Pat. No. 5,354,316 to Keimel, U.S. Pat.No. 5,314,430 to Bardy, U.S. Pat. No. 5,131,388 to Pless, and U.S. Pat.No. 4,821,723 to Baker et al., all hereby incorporated by referenceherein, each in its respective entirety.

FIGS. 4 and 5 illustrate one embodiment of IMD 10 and a correspondinglead set of the present invention, where IMD 10 is a PCD. In FIG. 4, theventricular lead takes the form of leads disclosed in U.S. Pat. Nos.5,099,838 and 5,314,430 to Bardy, and includes an elongated insulativelead body 100 carrying three concentric coiled conductors separated fromone another by tubular insulative sheaths. Located adjacent the distalend of lead 100 are ring electrode 102, extendable helix electrode 104mounted retractably within insulative electrode head 106 and elongatedcoil electrode 108. Each of the electrodes is coupled to one of thecoiled conductors within lead body 100. Electrodes 102 and 104 areemployed for cardiac pacing and for sensing ventricular depolarizations.At the proximal end of the lead is bifurcated connector 110 whichcarries three electrical connectors, each coupled to one of the coiledconductors. Elongated coil electrode 108, which is a defibrillationelectrode 108, may be fabricated from platinum, platinum alloy or othermaterials known to be usable in implantable defibrillation electrodesand may be about 5 cm in length.

The atrial/SVC lead shown in FIG. 4 includes elongated insulative leadbody 112 carrying three concentric coiled conductors separated from oneanother by tubular insulative sheaths corresponding to the structure ofthe ventricular lead. Located adjacent the J-shaped distal end of thelead are ring electrode 114 and extendable helix electrode 116 mountedretractably within an insulative electrode head 118. Each of theelectrodes is coupled to one of the coiled conductors within lead body112. Electrodes 114 and 116 are employed for atrial pacing and forsensing atrial depolarizations. Elongated coil electrode 120 is providedproximal to electrode 114 and coupled to the third conductor within leadbody 112. Electrode 120 preferably is 10 cm in length or greater and isconfigured to extend from the SVC toward the tricuspid valve. In oneembodiment of the present invention, approximately 5 cm of the rightatrium/SVC electrode is located in the right atrium with the remaining 5cm located in the SVC. At the proximal end of the lead is bifurcatedconnector 122 carrying three electrical connectors, each coupled to oneof the coiled conductors.

The coronary sinus lead shown in FIG. 4 assumes the form of a coronarysinus lead disclosed in the above cited '838 patent issued to Bardy, andincludes elongated insulative lead body 124 carrying one coiledconductor coupled to an elongated coiled defibrillation electrode 126.Electrode 126, illustrated in broken outline in FIG. 4, is locatedwithin the coronary sinus and great vein of the heart. At the proximalend of the lead is connector plug 128 carrying an electrical connectorcoupled to the coiled conductor. Elongated coil defibrillation electrode126 may be about 5 cm in length.

IMD 10 is shown in FIG. 4 in combination with leads 100, 112 and 124,and lead connector assemblies 110, 122 and 128 inserted into connectormodule 12. Optionally, insulation of the outward facing portion ofhousing 14 of IMD 10 may be provided using a plastic coating such asparylene or silicone rubber, as is employed in some unipolar cardiacpacemakers. The outward facing portion, however, may be left uninsulatedor some other division between insulated and uninsulated portions may beemployed. The uninsulated portion of housing 14 serves as a subcutaneousdefibrillation electrode to defibrillate either the atria or ventricles.Lead configurations other that those shown in FIG. 4 may be practiced inconjunction with the present invention, such as those shown in U.S. Pat.No. 5,690,686 to Min et al., hereby incorporated by reference herein inits entirety.

FIG. 5 is a functional schematic diagram of one embodiment of IMD 10 ofthe present invention. This diagram should be taken as exemplary of thetype of device in which various embodiments of the present invention maybe embodied, and not as limiting, as it is believed that the inventionmay be practiced in a wide variety of device implementations, includingcardioverter and defibrillators which do not provide anti-tachycardiapacing therapies.

IMD 10 is provided with an electrode system. If the electrodeconfiguration of FIG. 4 is employed, the correspondence to theillustrated electrodes is as follows. Electrode 150 in FIG. 5 includesthe uninsulated portion of the housing of IMD 10. Electrodes 108, 118,126 and 150 are coupled to high voltage output circuit 152, whichincludes high voltage switches controlled by CV/defib control logic 154via control bus 156. Switches disposed within circuit 152 determinewhich electrodes are employed and which electrodes are coupled to thepositive and negative terminals of a capacitor bank (which includescapacitors 158 and 160) during delivery of defibrillation pulses.

Electrodes 102 and 104 are located on or in the ventricle of the patientand are coupled to the R-wave amplifier 162, which preferably takes theform of an automatic gain controlled amplifier providing an adjustablesensing threshold as a function of the measured R-wave amplitude. Asignal is generated on R-out line 165 whenever the signal sensed betweenelectrodes 102 and 104 exceeds the present sensing threshold.

Electrodes 114 and 116 are located on or in the atrium of the patientand are coupled to the P-wave amplifier 164, which preferably also takesthe form of an automatic gain controlled amplifier providing anadjustable sensing threshold as a function of the measured P-waveamplitude. A signal is generated on P-out line 167 whenever the signalsensed between electrodes 114 and 116 exceeds the present sensingthreshold. The general operation of R-wave and P-wave amplifiers 162 and164 may correspond to that disclosed in U.S. Pat. No. 5,117,824 toKeimel et al., hereby incorporated by reference herein in its entirety.

Switch matrix 166 is used to select which of the available electrodesare coupled to wide band (0.5-200 Hz) amplifier 168 for use in digitalsignal analysis. Selection of electrodes is controlled by microprocessor170 via data/address bus 172, which selections may be varied as desired.Signals from the electrodes selected for coupling to bandpass amplifier168 are provided to multiplexer 174, and thereafter converted tomulti-bit digital signals by A/D converter 176, for storage in randomaccess memory 178 under control of direct memory access circuit 180.Microprocessor 170 may employ digital signal analysis techniques tocharacterize the digitized signals stored in random access memory 178 torecognize and classify the patient's heart rhythm employing any of thenumerous signal processing methodologies known to the art.

The remainder of the circuitry is dedicated to the provision of cardiacpacing, cardioversion and defibrillation therapies, and, for purposes ofthe present invention may correspond to circuitry known to those skilledin the art. The following exemplary apparatus is disclosed foraccomplishing pacing, cardioversion and defibrillation functions. Pacertiming/control circuitry 182 preferably includes programmable digitalcounters which control the basic time intervals associated with DDD,VVI, DVI, VDD, AAI, DDI and other modes of single and dual chamberpacing well known to the art. Circuitry 182 also preferably controlsescape intervals associated with anti-tachyarrhythmia pacing in both theatrium and the ventricle, employing any anti-tachyarrhythmia pacingtherapies known to the art.

Intervals defined by pacing circuitry 182 include atrial and ventricularpacing escape intervals, the refractory periods during which sensedP-waves and R-waves are ineffective to restart timing of the escapeintervals and the pulse widths of the pacing pulses. The durations ofthese intervals are determined by microprocessor 170, in response tostored data in memory 178 and are communicated to pacing circuitry 182via address/data bus 172. Pacer circuitry 182 also determines theamplitude of the cardiac pacing pulses under control of microprocessor170.

During pacing, escape interval counters within pacer timing/controlcircuitry 182 are reset upon sensing of R-waves and P-waves as indicatedby a signals on lines 165 and 167, and in accordance with the selectedmode of pacing on time-out trigger generation of pacing pulses by paceroutput circuitry 184 and 186, which are coupled to electrodes 102, 104,112 and 116. Escape interval counters are also reset on generation ofpacing pulses and thereby control the basic timing of cardiac pacingfunctions, including anti-tachyarrhythmia pacing. The durations of theintervals defined by escape interval timers are determined bymicroprocessor 170 via data/address bus 172. The value of the countpresent in the escape interval counters when reset by sensed R-waves andP-waves may be used to measure the durations of R-R intervals, P-Pintervals, P-R intervals and R-P intervals, which measurements arestored in memory 178 and used to detect the presence oftachyarrhythmias.

Microprocessor 170 most preferably operates as an interrupt drivendevice, and is responsive to interrupts from pacer timing/controlcircuitry 182 corresponding to the occurrence of sensed P-waves andR-waves and corresponding to the generation of cardiac pacing pulses.Those interrupts are provided via data/address bus 172. Any necessarymathematical calculations to be performed by microprocessor 170 and anyupdating of the values or intervals controlled by pacer timing/controlcircuitry 182 take place following such interrupts.

Detection of atrial or ventricular tachyarrhythmias, as employed in thepresent invention, may correspond to tachyarrhythmia detectionalgorithms known in the art. For example, the presence of an atrial orventricular tachyarrhythmia may be confirmed by detecting a sustainedseries of short R-R or P-P intervals of an average rate indicative oftachyarrhythmia or an unbroken series of short R-R or P-P intervals. Therate of onset of the detected high rates, the stability of the highrates, and a number of other factors known in the art may also bemeasured at this time. Appropriate ventricular tachyarrhythmia detectionmethodologies measuring such factors are described in U.S. Pat. No.4,726,380 issued to Vollmann, U.S. Pat. No. 4,880,005 issued to Pless etal., and U.S. Pat. No. 4,830,006 issued to Haluska et al., allincorporated by reference herein, each in its respective entirety. Anadditional set of tachycardia recognition methodologies is disclosed inthe article “Onset and Stability for Ventricular TachyarrhythmiaDetection in an Implantable Pacer-Cardioverter-Defibrillator” by Olsonet al., published in Computers in Cardiology, Oct. 7-10, 1986, IEEEComputer Society Press, pages 167-170, also incorporated by referenceherein in its entirety. Atrial fibrillation detection methodologies aredisclosed in Published PCT Application Ser. No. US92/02829, PublicationNo. WO92/18198, by Adams et al., and in the article “AutomaticTachycardia Recognition”, by Arzbaecher et al., published in PACE,May-June, 1984, pp. 541-547, both of which are incorporated by referenceherein in their entireties.

In the event an atrial or ventricular tachyarrhythmia is detected and ananti-tachyarrhythmia pacing regimen is desired, appropriate timingintervals for controlling generation of anti-tachyarrhythmia pacingtherapies are loaded from microprocessor 170 into the pacer timing andcontrol circuitry 182 via data bus 172, to control the operation of theescape interval counters therein and to define refractory periods duringwhich detection of R-waves and P-waves is ineffective to restart theescape interval counters.

Alternatively, circuitry for controlling the timing and generation ofanti-tachycardia pacing pulses as described in U.S. Pat. No. 4,577,633,issued to Berkovits et al., U.S. Pat. No. 4,880,005, issued to Pless etal., U.S. Pat. No. 4,726,380, issued to Vollmann et al., and U.S. Pat.No. 4,587,970, issued to Holley et al., all of which are incorporatedherein by reference in their entireties, may also be employed.

In the event that generation of a cardioversion or defibrillation pulseis required, microprocessor 170 may employ an escape interval counter tocontrol timing of such cardioversion and defibrillation pulses, as wellas associated refractory periods. In response to the detection of atrialor ventricular fibrillation or tachyarrhythmia requiring a cardioversionpulse, microprocessor 170 activates cardioversion/defibrillation controlcircuitry 154, which initiates charging of high voltage capacitors 158and 160 via charging circuit 188, under the control of high voltagecharging control line 190. The voltage on the high voltage capacitors ismonitored via VCAP line 192, which is passed through multiplexer 174 andin response to reaching a predetermined value set by microprocessor 170,results in generation of a logic signal on Cap Full (CF) line 194 toterminate charging. Thereafter, timing of the delivery of thedefibrillation or cardioversion pulse is controlled by pacertiming/control circuitry 182. Following delivery of the fibrillation ortachycardia therapy microprocessor 170 returns the device to q cardiacpacing mode and awaits the next successive interrupt due to pacing orthe occurrence of a sensed atrial or ventricular depolarization.

Several embodiments of appropriate systems for the delivery andsynchronization of ventricular cardioversion and defibrillation pulsesand for controlling the timing functions related to them are disclosedin U.S. Pat. No. 5,188,105 to Keimel, U.S. Pat. No. 5,269,298 to Adamset al., and U.S. Pat. No. 4,316,472 to Mirowski et al., herebyincorporated by reference herein, each in its respective entirety. Anyknown cardioversion or defibrillation pulse control circuitry isbelieved to be usable in conjunction with various embodiments of thepresent invention, however. For example, circuitry controlling thetiming and generation of cardioversion and defibrillation pulses such asthat disclosed in U.S. Pat. No. 4,384,585 to Zipes, U.S. Pat. No.4,949,719 to Pless et al., or U.S. Pat. No. 4,375,817 to Engle et al.,all hereby incorporated by reference herein in their entireties, mayalso be employed.

Continuing to refer to FIG. 5, delivery of cardioversion ordefibrillation pulses is accomplished by output circuit 152 under thecontrol of control circuitry 154 via control bus 156. Output circuit 152determines whether a monophasic or biphasic pulse is delivered, thepolarity of the electrodes and which electrodes are involved in deliveryof the pulse. Output circuit 152 also includes high voltage switcheswhich control whether electrodes are coupled together during delivery ofthe pulse. Alternatively, electrodes intended to be coupled togetherduring the pulse may simply be permanently coupled to one another,either exterior to or interior of the device housing, and polarity maysimilarly be pre-set, as in current implantable defibrillators. Anexample of output circuitry for delivery of biphasic pulse regimens tomultiple electrode systems may be found in the above cited patent issuedto Mehra and in U.S. Pat. No. 4,727,877 to Kallok, hereby incorporatedby reference herein in its entirety.

An example of circuitry which may be used to control delivery ofmonophasic pulses is disclosed in U.S. Pat. No. 5,163,427 to Keimel,also incorporated by reference herein in its entirety. Output controlcircuitry similar to that disclosed in U.S. Pat. No. 4,953,551 to Mehraet al. or U.S. Pat. No. 4,800,883 to Winstrom, both incorporated byreference herein in their entireties, may also be used in conjunctionwith various embodiments of the present invention to deliver biphasicpulses.

Alternatively, IMD 10 may be an implantable nerve stimulator or musclestimulator such as that disclosed in U.S. Pat. No. 5,199,428 to Obel etal., U.S. Pat. No. 5,207,218 to Carpentier et al., or U.S. Pat. No.5,330,507 to Schwartz, or an implantable monitoring device such as thatdisclosed in U.S. Pat. No. 5,331,966 issued to Bennet et al., all ofwhich are hereby incorporated by reference herein, each in itsrespective entirety. The present invention is believed to find wideapplication to any form of implantable electrical device for use inconjunction with electrical leads.

FIG. 6 is a perspective view of programmer unit 200 which includes thepresent invention. Programmer unit 200 has various features, includingouter housing 202, carrying handle 204, articulate display screen 206,RF head or stylus 208, and analyzer 210.

Display unit 206 is disposed on the upper surface of housing 202.Display screen 206 folds down in a closed position when programmer 200is not in use, thereby reducing the size of programmer 200 andprotecting the display surface of display screen 206 duringtransportation and storage. In the perspective view of FIG. 6,programmer 200 is shown with articulate display screen 206 having beenlifted up into one of a plurality of possible open positions such thatthe display area is visible to a user situated in front of programmer200. Display screen 206 is preferably an LCD or electroluminescent type,characterized by being relatively thin as compared to a cathode ray tubedisplay, or the like. Display screen 206 is operatively coupled tocomputer circuitry disposed within housing 202 and is adapted to providea visual display of graphics and/or numerical and alphanumeric dataunder control of the computer circuitry.

In accordance with one aspect of the present invention, display screen206 is provided with touch-sensitivity capability, such that a user caninteract with the internal computer by touching the display area ofdisplay screen 206 with stylus 208. It is believed that those ofordinary skill in the computer will be familiar with touch-sensitivitydisplay technology, and the details of implementation of such displaywill not be described further herein. Display screen 206 is the primaryinput medium for programmer 200, and therefore preferably has sufficientresolution to support operations including selection, gestures,annotation, and character recognition.

Analyzer 210, which in prior art devices was a separate unit capable ofconnection to programmer unit 200 only via connecting cables, provides amedium for an operator to run a series of diagnostic tests during animplantation procedure of an IMD, such as IMD 10 previously discussed.For example, a continuous-time waveform or a single complex waveform canbe analyzed by analyzer 210 and displayed on display screen 206 from avariety of implanted leads, such as a lead positioned in an atrium orventricle of heart 8 (shown in FIGS. 1, 2 and 4).

FIG. 7 shows block diagram 218 encompassing various features of thepresent invention. Analyzer 210, as previously discussed, provides amedium for an operator to run a series of diagnostic tests during animplantation procedure of an IMD, such as IMD 10. Analyzer 210 receivesa “raw” cardiac electrogram signal from the leads used to later connectIMD 10 to heart 8 of patient 220. Analyzer 210 includes a marker channeltelemetry system which utilizes latches to store event information andforms marker codes. The marker codes indicate the occurrence of specificevents such as sensed and paced events found in the electrogram signal,for example, the occurrence of a P-wave. Thus, analyzer 210 conditionsthe electrogram signal received from patient 210 by inserting markersinto the electrogram signal. Examples of a marker channel telemetrysystem are disclosed in U.S. Pat. No. 4,374,382 to Markowitz, herebyincorporated by reference herein in its entirety.

The marker signal is supplied from analyzer 210 to microprocessor 224.Microprocessor 224 performs numerous functions with the received markedelectrogram signal. One such function is the addition of amplitudeinformation to the marked electrogram signal. Another function performedby microprocessor 224 is the continual reading of the marked electrogramsignal. Microprocessor 224 performs a routine which monitors the contentof the continuous electrogram signal for marker information. If a markeris detected that indicates the start of a cardiac waveform complex(P-wave), the information (the “raw” signal accompanied by theadditional information) in the continuous signal proceeding the markerand following the marker is captured into a display buffer.

An operator, utilizing programmer unit 200, shown in FIG. 6, has achoice between displaying one or more continuous-time waveforms ordisplaying a single complex waveform. For purposes of this application,a single complex waveform is defined as a portion of the continuous-timewaveform immediately before and after a marker. If a continuous waveformis chosen, microprocessor 224 enables continuous-time waveform display226. Conversely, if a single complex waveform is desired, microprocessor224 enables single complex waveform display 228.

When operating in the continuous-time waveform mode, continuous-timewaveform display 226 is activated. An example of what is displayed ondisplay screen 206 in this mode is shown in FIGS. 8 and 9.

FIG. 8 shows various signals 242, 244, 246, 248, and 250 which arecontinuously scrolling across the display screen from left to right.Display 240 of FIG. 8 also shows timing information 252 and 254 toassist an operator in evaluating the various waveforms, as well astoolbar 256. Toolbar 256 includes freeze button 258, continuous-timewaveform icon 260, single complex cardiac waveform 262, and otherfeatures not relevant to the present invention. While toolbar 256 isshown in FIGS. 8-11 on the right portion of display screen 206, it isdone for illustrative purposes only and the location of the toolbar 256can be altered without deviating from the present invention.

FIG. 9 differs from FIG. 8 in that display screen 206 has been dividedinto two separate compartments, specifically continuous-time modedisplay 26A and continuous-time mode control 26B. Through utilization ofcontinuous-time display control 264B, an operator can reprogram variousaspects of programmer 200 and view the corresponding change in waveformsvia continuous-mode display 264A.

During an implantation procedure, wherein an implantable medical device,such as a pacemaker, is implanted into patient 220, a prior art displayscreen would display continuous signals, such as those shown in FIGS. 8and 9, constantly scrolling across display screen 206. Due to theconstant movement of the signals across display screen 206, it isextremely difficult for an operator to analyze this information todetermine if a pacing or sensing lead is properly positioned within apassageway of a patient.

FIG. 10 discloses display 240A showing a graph of single complexwaveform 272 representative of a portion of one of the continuous-timewaveforms shown in FIGS. 8 and 9. Waveform 272 is shown in atime-expanded format so that the shape of waveform 272 can be analyzed.Additionally, amplitude information is displayed for greater analysis.

When operating in the single complex waveform mode, single complexwaveform display 228 of FIG. 7 is activated and display screen 206 ofprogrammer unit 200 displays a portion of the received electrogramsignal corresponding to the information in the stream immediatelypreceding and following a marker. This information is centered ondisplay screen 206. An example of what is displayed on display screen206 is shown in FIG. 10. Microprocessor 224 continuously updatesdisplayed waveform 272 at regular intervals. Specifically,microprocessor 224 will provide an updated waveform to display screen206 stored in a display buffer within microprocessor 224 at regularintervals.

One aspect of the present invention is to provide a readable singlecomplex waveform representing a portion of the received electrogramsignal adjacent a marker which can be analyzed by the operator. Thesingle complex waveform must be displayed in a constant location ondisplay screen 206 and updated at a rate which can be processed by theoperator. Thus, with the present invention, microprocessor 224 monitorsa heart rate of the patient. If the heart rate is less than 90 beats perminute, the single cardiac waveform is updated with each heartbeat. Ifthe heartbeat of the patient is between 90 and 160 heartbeats perminute, the single cardiac waveform is updated every other heartbeat,and if the patient's heartbeat is greater than 160 beats per minute, thesingle complex waveform is updated every third heartbeat.

Single complex waveform display 228 (of FIG. 7), which is displayed ondisplay screen 206 in FIGS. 10 and 11, provides a means for an operatorto evaluate the shape of a waveform, as well as its magnitude, thusenabling an operator to determine if a specific lead is properlypositioned within a passageway of heart 8, during an implant procedure.

An additional feature of the present invention includes frozen display230 (shown in FIG. 7). Frozen display 230 permits a user to “freeze” orhold a particular single complex waveform on display screen 206 fordetailed evaluation via freeze button 258 (of FIGS. 10 and 11). The usercan also print out the frozen display via printer 232.

With the present invention, the operator may utilize icons 260 and 262,shown in FIGS. 8 and 9, to facilitate a proper reading of the displayedsignals. In accordance with the present invention, single complexwaveform icon 262 permits a user to view a portion of a single displayedwaveform corresponding to a single heartbeat of the patient. Byutilizing icon 262, display screen 206 will display the graph shown inFIG. 10. During an implant procedure, it is desirous to view a singlewaveform corresponding to a single lead in order to determine properlocation of the lead. An operator can modify the position of a specificlead and analyze a time, expanded continuously updated waveform. Theconfiguration of the waveform aids the operator in determining thedesired location of the lead. Continuous-time waveform icon 260 returnsdisplay screen 206 to the continuous-time waveform display.

As shown in FIG. 10, display 240A includes toolbar 256. Toolbar 256further includes freeze icon 258, continuous-time waveform icon 260, andsingle complex cardiac waveform 262. As previously discussed, freezeicon 258 permits an operator to continuously view a specific waveform.Continuous-time waveform 260 and single complex waveform 262 act as atoggle switch which permits an operator to display the desired waveform.EGM panel 266 notifies the operator of the source of the signal beingviewed, such as a signal from a lead within an atrium or ventricle ofthe patient, and permits switching between the two signals.

FIGS. 11 and 12 shows display 240B and 240C which is virtually identicalto display 240A shown in FIG. 10. However, the display shown in FIGS. 11and 12 includes heartbeat icon 268 which will appear on display screen206 each time a marker is sensed by microprocessor 224 representing aheartbeat. As previously discussed, waveform 272 will be updated everyfirst, second, or third heartbeat depending upon the heart rate of thepatient. If the heart rate of the patient is less than 90 beats perminute, signal 272 will be updated with each heartbeat. If the heartrate of the patient is between 90 and 160 beats per minute, signal 272will be updated every other heartbeat. If the heart rate of the patientis greater than 160 beats per minute, waveform 272 will be updated everythird heart beat.

An additional feature of the present invention is the ability of anoperator to graphically assess the relationship of cardiac events to asensitivity threshold of IMD 10, thereby providing a means to assess thedegree of sensing margin for detected atrial and ventricular events.This feature is also is useful for assessing the degree of marginavailable for rejecting non-desired events, such as far-field signalsand ventricular t-waves. More specifically, the present inventionprovides a graphical display of the sensitivity threshold, shown inFIGS. 11 and 12 as sensitivity threshold line 270. Sensitivity thresholdline 270 is positioned at the graphical location representing apredetermined and adjustable voltage. Prior art references fail in theirteachings to disclose a graphical display of the sensitivity thresholdpositioned across a display screen and in conjunction with a beat of awaveform, as shown in FIGS. 11 and 12.

It is critical that later implanted IMD 10, through its pacing andsensing leads, is capable of properly detecting electrical impulses fromheart 8 of a patient, while filtering out unwanted noise, such asfar-field signals. Later implanted IMD 10 must sense the intrinsicactivity of heart 8 in order to properly operate.

As shown in FIGS. 11 and 12, waveform 272, which represents a simulatedelectrical signal simulating a heartbeat of a patient, has a positivepeak point which is greater than sensitivity threshold line 270. Indetermining whether the sensitivity threshold of a particular unit isproperly set, an operator would review the graphical representationshown in FIGS. 11 and 12. For proper location, the peak of electricalsignal 272 must have a voltage greater than sensitivity threshold line270. However, if sensitivity threshold line 270 is set at too low of avoltage, unwanted noise will be detected and a later implanted IMD maynot function properly. The sensitivity threshold can be adjusted tocorrespond to a desired output through use of a display control, such asdisplay control 264B, shown in FIG. 9. In FIG. 11, the sensitivitythreshold is set at 0.50 millivolts, while in FIG. 12, the sensitivitythreshold is set at 2.50 millivolts. In both instances (FIGS. 11 and12), the sensitivity threshold is adequately set since the peak ofelectrical signal 272 has a voltage greater than sensitivity thresholdline 270, but sensitivity threshold line 270 is not positioned to low toallow unwanted noise.

FIG. 13 is a flow chart disclosing the steps encompassing thesensitivity threshold feature of the present invention. The elementsshown and described in FIG. 13 are located within a programmer unit 200(shown in FIG. 6). Electrode 300 would be attached to a specific sensingor pacing lead needing diagnostic evaluation. Filter/protection 302would receive a signal from sense electrode 300. The purpose offilter/protection 302 is to simulate the characteristics of the inputsensing portion of IMD 10. This ensures that the sensing characteristicsbeing analyzed will correspond with the sensing characteristics of laterimplanted IMD 10. Amplifier 304 receives a signal from filter/protection302 and provides an amplified signal to either display 206 or rectifier306. Thus, display 206 can display either a rectified or non-rectifiedsensitivity threshold.

In the claims, means-plus-function clauses are intended to cover thestructures described herein as performing the reciting function and notonly structural equivalence but also equivalent structures. For example,although a nail and a screw may not be structurally equivalent in that anail employs a cylindrical surface to secure wooden parts together,whereas a screw employs a helical surface, in the environment offastening wood parts, a nail and a screw are equivalent structures.

Although specific embodiments of the invention have been set forthherein in some detail, it is understood that this has been done for thepurposes of illustration only and is not to be taken as a limitation onthe scope of the invention as defined in the appended claims. It is tobe understood that various alterations, substitutions, and modificationsmay be made to the embodiment described herein without departing fromthe spirit and scope of the appended claims.

What is claimed is:
 1. A system for graphically displaying informationreceived from at least one lead positioned within a passageway of aheart related to an implantable medical device, the system comprising:an analyzer for receiving the electrogram signal from the electricallead and for locating and marking desired characteristics of theelectrogram signal with a plurality of markers to produce a markedelectrogram signal; a processor for receiving the marked electrogramsignal from the analyzer, for recognizing the marked desiredcharacteristics of the electrogram signal, and for inserting amplitudeinformation into the marked electrogram signal; a display buffer formomentarily capturing a portion of the electrogram signal adjacent to asingle marker; updating means for continuously updating the capturedportion of the electrogram signal; a selection switch for selecting aselected signal between the electrogram signal received from theelectrical lead and the captured portion of the electrogram signalstored in the display buffer; a sensitivity threshold control forcontrolling a sensitivity threshold; and a display controlled by theprocessor for displaying the selected signal and for graphicallydisplaying the sensitivity threshold superimposed on the selectedsignal.
 2. The system of claim 1, wherein the processor centers theselected signal on the display.
 3. The system of claim 1, wherein theprocessor displays the amplitude information on the display.
 4. Thesystem of claim 1, wherein the processor further comprises: monitoringmeans for monitoring a heart rate; and comparing means for comparing theheart rate to a predetermined set of ranges.
 5. The system of claim 4,wherein the updating means updates the captured portion of theelectrogram signal with every heartbeat.
 6. The system of claim 4,wherein the updating means updates the captured portion of theelectrogram signal with every second heartbeat.
 7. The system of claim4, wherein the updating means updates the captured portion of theelectrogram signal with every third heart beat.
 8. The system of claim 1and further comprising a hold icon located on the display and controlledby the processor for holding the selected signal and the sensitivitythreshold on the display.
 9. The system of claim 8 and furthercomprising a print icon located on the display and controlled by theprocessor for printing the selected signal and the sensitivity thresholdheld on the display.
 10. The system of claim 1, wherein the displaydisplays the selected signal and the sensitivity threshold in atime-expanded format.
 11. A programmer for graphically displayinginformation received from at least one lead positioned within apassageway of a heart and related to an implantable medical device, theprogrammer comprising: an analyzer for receiving an electrogram signaland for locating and marking desired characteristics of the electrogramsignal with a plurality of markers to produce a marked electrogramsignal; a processor for receiving the electrogram signal from theanalyzer and for recognizing the marked desired characteristics of theelectrogram signal, the processor also receiving sensitivity thresholdinformation; and a display controlled by the processor for graphicallydisplaying information representing a portion of the electrogram signalimmediately adjacent to a single marker and for graphically displaying asensitivity threshold.
 12. The programmer of claim 11, wherein theprocessor centers the portion of the electrogram signal immediatelyadjacent to a single marker on the display.
 13. The programmer of claim11, wherein the processor inserts amplitude information onto theelectrogram signal.
 14. The system of claim 13, wherein the processordisplays the amplitude information on the display.
 15. The programmer ofclaim 11, wherein the processor further comprises: monitoring means formonitoring a heart rate; and comparing means for comparing the heartrate to a predetermined set of ranges.
 16. The programmer of claim 15,wherein the display displays an updated portion of the electrogramsignal immediately adjacent to a single marker with every heartbeat. 17.The programmer of claim 15, wherein the display displays an updatedportion of the electrogram signal immediately adjacent to a singlemarker with every second heartbeat.
 18. The programmer of claim 15,wherein the display displays an updated portion of the electrogramsignal immediately adjacent to a single marker with every thirdheartbeat.
 19. The programmer of claim 11, and further comprising a holdicon located on the display and controlled by the processor for holdingthe electrogram signal immediately adjacent to a single marker and forholding the sensitivity threshold.
 20. The programmer of claim 19, andfurther comprising a print icon located on the display and controlled bythe processor for printing the portion of the electrogram signalimmediately adjacent to a single marker and for printing the sensitivitythreshold.
 21. The programmer of claim 11, further comprising a userinput, wherein the processor receives updated sensitivity thresholdinformation based upon an input from a user.
 22. A method of graphicallydisplaying information relating to an electrogram signal received fromat least one lead positioned within a passageway of a heart and relatedto an implantable medical device, the programmer comprising: analyzingthe electrogram signal to locate desired characteristics of theelectrogram signal; inserting a plurality of markers into theelectrogram signal at a location of the desired characteristics;filtering a sensitivity threshold signal received from a lead to removeunwanted noise; amplifying the filtered sensitivity threshold signal;and displaying a portion of the electrogram signal immediately adjacentto a single marker and graphically displaying a sensitivity thresholdlevel representing the amplified and filtered sensitivity thresholdsignal.
 23. The method of claim 22, wherein the step of displaying aportion of the electrogram signal further comprises: centering theportion of the electrogram signal immediately adjacent to a singlemarker on the display.
 24. The method of claim 22 and furthercomprising: inserting amplitude information into the electrogram signal.25. The method of claim 24, wherein the step of displaying a portion ofthe electrogram signal further comprises: displaying the amplitudeinformation.
 26. The method of claim 22 and further comprising:monitoring a heart rate; and comparing the heart rate to a predeterminedrange.
 27. The method of claim 26 and further comprising: displaying theportion of the electrogram signal immediately adjacent to a singlemarker after each heartbeat.
 28. The method of claim 26 and furthercomprising: displaying the portion of the electrogram signal immediatelyadjacent to a single marker after every second heartbeat.
 29. The methodof claim 26 and further comprising: displaying the portion of theelectrogram signal immediately adjacent to a single marker after everythird heartbeat.
 30. The method of claim 22 and further comprising:maintaining the displayed portion of the electrogram signal and thesensitivity threshold level on the display.
 31. The method of claim 22and further comprising: printing the displayed portion of theelectrogram signal and the sensitivity threshold level.